What would happen if we killed all the mosquitoes?

Bill Gates called mosquitoes “the deadliest animal in the world” for their incessant spreading of deadly diseases like malaria, which killed an estimated 429,000 in 2015 alone. Nearly half the world lives at risk of the disease, said the World Health Organization, which made the estimate.

Depending on where you live, mosquitoes may range from an itch-inducing annoyance to a constant threat. That’s led scientists to ask: What if we killed them all?

We just don’t know, many of those experts have concluded. But they can imagine.

More than 3,500 mosquitoes species exist, but only a few affect our health. The Anopheles gambiae carries malaria, for example. The Aedes aegypti came to the U.S. aboard slave ships, spreading yellow fever and, as seen last year, Zika.

So we need not end all mosquitoes to reduce mosquito-related deaths, as Cameron Webb, an etymologist at the University of Sydney, told Motherboard last year. And that may be preferable, said Webb, who had “little doubt” their full extinction could have indirect effects.

The food chain would likely be OK

Mosquitoes swarming in the air at summer. (Photo: TT, Getty Images/iStockphoto)

Mosquitoes act as a key food source for fish, birds, lizards, frogs and bats and other animals. Yet no species relies solely on them, as the journal Nature found in 2010. Other insects could flourish in their place, and it seems most species would find alternatives to eat. And while mosquitoes do help pollinate thousands of plants, Janet McAllister, an entomologist with the Centers for Disease Control, told Nature that mosquito pollination isn’t critical to any plants humans rely on.

Phil Lounibos, a University of Florida entomologist, has said that whatever insect rises up to replace mosquitoes could prove “equally, or more, undesirable from a public health viewpoint,” as he told BBC last year. Science writer David Quammen has suggested that mosquitoes protected tropical rainforests in which they thrive, keeping human beings —and deforestation—at bay.

Inevitably, the absence of mosquitoes would shift our ecosystems. But would those shifts be drastic or long lasting? Again, we don’t know for sure. Ecosystems are complex, and experts disagree.

One drastic change we would see: Hundreds of thousands would not die malaria each year, most of which being children under five. Add to that the reduction of roughly 55,000 annual deaths reducible from dengue fever or yellow fever, for which the Aedes aegypti is the main carrier.

That human toll has researchers pondering how to rid the earth of (at least some) mosquitoes. British researchers developed genetically modified Aedes aegypti mosquitoes that self-destruct, though the process is costly and uncertain.

“Global elimination of an entire species, I think, is a little far-fetched,” said Steven Juliano, an Illinois State University ecologist, to the Smithsonian. He added: “I think they have a good chance of reducing local populations, maybe even eradicating a species in a locality.”